1. Field of the Invention
This invention relates to equipment for testing in situ the trip functions of circuit breakers which may have a range of rated currents and/or line voltages.
2. Background Information
Circuit breakers in some applications are tested periodically to assure reliability. This is particularly so in aircraft electrical systems. It is preferable that the circuit breakers be tested in their installed state. The job is made more difficult by the high density of these very small circuit breakers and the fact in any one aircraft system, the breakers can have a range of current ratings. Furthermore, aircraft circuit breakers are now being offered with multiple trip functions.
U.S. Pat. No. 6,744,260 discloses a tester employing various power resistors for testing delayed trip and arc fault trip functions. A suitcase enclosure encloses the portable tester. A test selector switch includes one position for a thermal trip test, a second position for a delayed trip test, and a third position for an arc fault test. Due to power dissipation requirements for thermal overload testing, a separate, high-power, less portable module containing high power output stages and load resistors is connected to a printed circuit board though a connector. A controller includes a full wave rectifier so that the current through the load elements is direct current. In this case, a zero crossing detector synchronizes turning on of the electronic switches with half cycles of the alternating current.
There is a need for an improved circuit breaker tester that is portable, relatively small, and relatively light-weight for use in situ testing of circuit breakers, and particularly, installations with circuit breakers having a range of current and/or line voltage ratings.
There is room for improvement in testers for circuit breakers.